A gas sensor scheme for CO based on optical-feedback linear-cavity enhanced absorption spectroscopy

Trace gases, especially some toxic trace gases, such as carbon monoxide, are of great value for high-precision detection of their concentration in environmental, safety, and health monitoring. To accurately measure CO gas, a novel spectral technique scheme is developed and demonstrated based on cavity-enhanced absorption spectroscopy with a high-quality linear cavity. The scheme can achieve the equal noise absorption sensitivity of 2.37 × 10−8 cm−1 at the cavity loss of 186 ppm, which can achieve the concentration measurement of 11.7 ppm of CO gas at 1564 nm in the near-infrared band. This approach has the potential for expansion to other gas concentration detection applications and can achieve ppb-ppt level concentration detection. •In this paper, a high-isolation spatial optical isolator was employed to eliminate all feedback light at the input mirror of the linear cavity, which allowed only the transmitted light from the output end mirror of the resonator to provide the necessary optical feedback effect. It effectively eliminated the influence of the first-order reflected light at the incident end of the optical resonator on the performance of the laser while further enhancing the coupling efficiency between the laser and cavity.